Polyvinylamine is a useful substance widely used as a flocculant, papermaking chemical, fiber treatment agent, paint additive, etc. High-molecular weight polyvinylamine is said to be particularly effective in cases of using as a flocculant in wastewater treatment or as a papermaking chemical in the paper manufacturing industry.
Generally, polyvinylamine is obtained by hydrolyzing the entirety or part of a polymer or copolymer of N-vinylcarboxamide (hereinafter both are collectively noted as (co)polymer), under the presence of acid or alkali. However, upon high-molecular weight polyvinylamine being made into an aqueous solution, there are problems such as being difficult to handle due to becoming very high viscosity, while handling becomes easy if diluted, but leads to cost increases in production and transport.
Conventionally, a method of making an aqueous solution by alkaline hydrolysis of polymer powder of N-vinylcarboxamide has been proposed, and in this case, it is said that a high-molecular weight product having a reduced viscosity of at least 9 is favorable as the (co)polymer of N-vinylcarboxamide (Patent Document 1). However, the obtained aqueous solution has high viscosity, and thus the handling is very difficult. In addition, an aqueous solution standing adiabatic polymerization method has been proposed as a polymerization method of N-vinylcarboxamide (Patent Document 2). However, in this proposal, the conversion method to polyvinylamine and functionality thereof are not explained.
Hydrolysis of N-vinylcarboxamide (co)polymer to polyvinylamine carried out at alkaline conditions is advantageous in industry. In other words, in acidic hydrolysis, corrosion resistance is required in all of the equipment plumbing related to production, transport, storage and use; whereas, at alkaline conditions, it is possible to use device plumbing made from normal steel and stainless steel.
In addition, solutions are advantageous as the product form. In other words, in the production of a powder finished product, a powder drying process is essential; however, the finished product deteriorates if the polyvinylamine is heated to high temperature, and the solubility of the finished product worsens. Such deterioration is a very important problem particularly in papermaking chemicals which require high solubility. Furthermore, with powders, equipment for dissolving upon use is necessary.
For the above-mentioned reasons, it is preferable to be alkaline and a uniform solution state as the product form, and this matter has already been known (Patent Document 1). However, countermeasures against aqueous solutions of high-molecular weight polyvinyl amine becoming very high viscosity have not been proposed.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2004-27015    Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2010-59220